Substrates, particularly substrates formed of polymer materials, have often been used for printed circuit boards in which an appropriate pattern of conductive paths are formed thereon so that circuit components can be soldered thereto to form an electrical circuit for use in electrical equipment. Methods for forming such conductive paths can be generally classified as additive processes or subtractive processes.
In the additive process approach the polymer substrate is treated in such a way that conductive material, such as metallic copper, is deposited thereon only at those locations where a conductive path is intended to exist in the finished circuit. In the subtractive process approach a conductive material, such as copper, is initially deposited over the entire substrate surface area and is then subsequently removed, as by suitable etching processes, for example, from the areas that are to remain non-conductive. In each approach the overall conductive pattern which represents the circuit pattern is effectively produced substantially at the same time. Such techniques, moreover, are normally suitable only for the production of circuits on two dimensional, i.e., flat, surfaces.
It is desirable to find a method and apparatus by which conductive paths can be formed in a simpler manner, and which method and apparatus can be readily adapted for the formation thereof on three-dimensional surfaces. Such method need not provide for the simultaneous formation of the entire conductive pattern.